body {
    font-family: Arial, sans-serif;
    background-color: #f0f0f0;
    margin: 0;
    padding: 0;
}

#center {
    width: 50%;
    margin: 50px auto;
    padding: 20px;
    background-color: #ffffff;
    border: 1px solid #ccc;
    border-radius: 10px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
    text-align: center;
}

#center h2, #center h1 {
    color: #333;
    margin: 0 0 20px;
}

#center table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 20px;
}

#center table, #center th, #center td {
    border: 1px solid #ddd;
}

#center th, #center td {
    padding: 12px;
    text-align: left;
}

#center th {
    background-color: #f4f4f4;
}

#center tr:nth-child(even) {
    background-color: #f9f9f9;
}

#center tr:hover {
    background-color: #f1f1f1;
}

#center a {
    color: #007BFF;
    text-decoration: none;
    margin: 0 10px;
}

#center a:hover {
    text-decoration: underline;
}

#center .operation {
    text-align: right;
}